1. Field of the Invention
This invention relates to an automatic photographing apparatus in a camera having the functions of presetting a photographing starting condition, and effecting photographing when said condition is satisfied.
2. Related Background Arts
There are known some cameras which preset a photographing starting condition and automatically start photographing after the condition is satisfied.
One such automatic photographing camera is disclosed, for example, in Japanese Utility Model Publication No. 64-4095 which presets a photographing distance and automatically effects photographing when this preset photographing distance coincides with a detected object distance.
In this automatic photographing camera, if a photographing distance is preset, when the camera is used, for example, in the fashion of self-timer photographing, the preset photographing distance coincides with a detected object distance if a photographer (as object) lies at the preset photographing distance, and therefore photographing is automatically effected.
According to such a prior-art automatic photographing camera, however, if the preset photographing distance does not coincide with the detected object distance, photographing will not take place forever. That is, when the camera is used in the fashion of self-timer photographing, there has been the problem that even if the photographer himself thinks that he lies at the preset photographing distance, the preset photographing distance is not coincident with the detected object distance and therefore, photographing does not start forever.
Also, as a second one, a camera having the so-called self-timer function is designed such that when a self-timer is caused to start its time counting operation, release takes place when a predetermined time has elapsed. However, if a third person should cross the space between the object and the camera immediately before the predetermined time elapses and release takes place, the third person will also be photographed, and photographing will have to be effected again. For example, according to Japanese Laid-Open Patent Application No. 2-37335, it has been proposed to memorize the object distance immediately after the timer operation is started, and to permit release when the measured range value immediately after the termination of the timer operation coincides with said memorized value, but to prohibit release when the former value does not coincides with the latter value. If this is done, release will take place when the third person leaves the object field and therefore, failure in photographing will be prevented.
This proposal, however, has suffered from the problem that photographing takes much time because if a main object to be originally photographed moves or sways to the front or the rear or to right or left, the measured range value does not coincide with the memorized value and release is not readily permitted.
Further, as a third one, a camera having the focus locking function is designed such that the focus thereof is locked to a false object, whereafter the camera is turned to an original object and when the original object is at a position whereat it can be photographed in a locked focus state, release is automatically effected. Such a technique is disclosed, for example, in Japanese Utility Model Publication No. 64-4095.
Also, for example, Japanese Laid-Open Patent Application No. 3-212635 or Japanese Laid-Open Patent Application No. 3-213838 proposes that the release operation be started when the measured range value at the start of the sequence of the auto self-timer mode and the measured range value thereafter vary.
However, of these apparatuses, in the former, the in-focus state is not obtained when an object is not in the depth of field at a set distance and thus, photographing is not effected. This has led to the possibility of the shutter chance being missed.
Also, the latter has suffered from the problem that for example, when a passerby crosses the front of an original object, the release operation is started at a timing differing from that intended by the photographer.
Furthermore, the above-mentioned Japanese Laid-Open Patent Application No. 2-37335 discloses a camera in which the distance to an object in a distance measuring area set in a portion of a predetermined photographing area is measured at least twice during the time counting by a self-timer and when the object distance measured later does not coincide with the object distance measured earlier, the time counting by the timer is interrupted and at a point of time whereat the object distance restores the original one, the time counting is restarted and photographing is effected after the lapse of a predetermined time. According to such a camera, when a passerby, an automobile or the like crosses the front of the object in the distance measuring area, the time counting by the timer is interrupted until such an invading body comes out of the distance measuring area. Accordingly, if the remaining time from the restart of the time counting by the timer till photographing is set to a value greater than the time expected to be required for the invading body which has come out of the distance measuring area to frame out, the invading body will be prevented from being photographed. The time necessary for the invading body to frame out may be determined with man's pace which is guessed to be slowest of all invading bodies as the standard. In the example shown in the above-mentioned publication, the remaining time from after the restart of the time counting till photographing is indiscriminately set to two seconds.
However, when the time from the restart of the time counting by the timer till photographing is made constant as described above, the following problems will arise.
A first problem arises in a camera in which the angle of field of a photo-taking lens is variable. For example, in a camera with a multifocus lens, when the angle of field of a photo-taking lens widens, the time required for an invading body which has come out of the distance measuring area to frame out becomes long, and when the angle of field becomes narrow, the time required for the invading body to frame out becomes short. Therefore, to prevent the invading body from being photographed irrespective of the magnitude of the angle of field, it is necessary to determine the remaining time from the restart of the time counting till photographing with the time required for the invading body to frame out when the angle of field is widest as the standard, and as a result, when the angle of field becomes narrow, the remaining time from the restart of the time counting till photographing becomes wastefully long.
A second problem arises because the passage position of the invading body is not always fixed. Even if there is no change in the angle of field, the time required for the invading body to frame out differs depending on the distance from the photo-taking lens at which the invading body passes, and when the invading body crosses just the front of the object, a long time is required, and when the invading body crosses just the front of the photo-taking lens, a short time is only required. Accordingly, if the remaining time after the restart of the time counting is determined with the time when the invading body crosses just the front of the object as the standard, there will be a waste time when the invading body crosses near the photo-taking lens.
As described above, automatic photographing apparatus in cameras designed such that a condition regarding an object such as the object distance or the object depth is preset and photographing is effected when this condition is satisfied are already known, but they have suffered from the inconvenience that unless the preset condition is satisfied, photographing is not effected, whereby the shutter chance is missed, or photographing differing from that intended by the photographer is effected.